Abstract

Background : One of the virulence factor of bacteria is the colonization which depend on the growth rate. Multiresistant bacteria was believed to have a slower growth rate than non-multiresistant bacteria. Aim :To investigate whether there was differences in doubling time of multiresistant and non-multiresistant strain of MRSA. Method : We obtained susceptibility profile to eight classes of antibiotics. The calculation of doubling time was performed as an overnight of bacterial cultures were diluted 1 : 100 in 5 mL of BHI medium and grown for 3 hours at 37°C, 180 rpm. These cultures were seeded at a 1:100 dilution in another 5 mL BHI medium and incubated at 37°C,180 rpm for futher 4 hours. Optical density was measured every 30 until 4 hours. Values were converted into log2 values, and the doubling time was calculated as the reciprocal of the slope. Results :The mean of doubling time of multiresistant strain of MRSA was 27.9 + 5.80 minutes, whereas non-multiresistant strain of MRSA was 22.3 + 0.99 minutes (p&lt;0.05). In addition, the logarithmic phase was different significantly between groups (p&lt;0.05). There was a correlation between the duration of logarithmic phase and doubling time (p&lt;0.05). Conclusion :The doubling time of multiresistant strain of MRSA was significantly longer than the doubling time of non-multiresistant strain of MRSA.